Thermal Management System for Multi-Chip-Module and Associated Methods

ABSTRACT

A plurality of lid structures include at least one lid structure configured to overlie one or more heat sources within a multi-chip-module and at least one lid structure configured to overlie one or more temperature sensitive components within the multi-chip-module. The plurality of lid structures are configured and positioned such that each lid structure is separated from each adjacent lid structure by a corresponding thermal break. A heat spreader assembly is positioned in thermally conductive interface with the plurality of lid structures. The heat spreader assembly is configured to cover an aggregation of the plurality of lid structures. The heat spreader assembly includes a plurality of separately defined heat transfer members respectively configured and positioned to overlie the plurality of lid structures. The heat spreader assembly is configured to limit heat transfer between different heat transfer members within the heat spreader assembly.

CLAIM OF PRIORITY

This application claims priority under 35 U.S.C. 119(e) to U.S.Provisional Patent Application No. 62/637,357, filed Mar. 1, 2018, thedisclosure of which is incorporated herein by reference in its entiretyfor all purposes.

BACKGROUND 1. Field of the Invention

The present invention relates to optical data communication.

2. Description of the Related Art

Optical data communication systems operate by modulating laser light toencode digital data patterns. The modulated laser light is transmittedthrough an optical data network from a sending node to a receiving node.The modulated laser light having arrived at the receiving node isde-modulated to obtain the original digital data patterns. Therefore,implementation and operation of optical data communication systems isdependent upon having reliable and efficient laser light sources andoptical processing devices. Also, it is desirable for the laser lightsources and optical processing devices of optical data communicationsystems to have a minimal form factor and be designed as efficiently aspossible with regard to expense and energy consumption. Also, in someoptical data processing systems, one or more temperature sensitivedevices, such as optical devices and/or optoelectronic devices, may bepositioned in proximity to one or more heat generating devices. Heatemanating from the one or more heat generating devices should be managedto avoid adversely affecting operation of the one or more temperaturesensitive devices. It is within this context that the present inventionarises.

SUMMARY

In an example embodiment, a thermal management system for amulti-chip-module is disclosed. The thermal management system includes aplurality of lid structures, including at least one lid structureconfigured to overlie one or more heat sources within themulti-chip-module, and at least one lid structure configured to overlieone or more temperature sensitive components within themulti-chip-module. The plurality of lid structures are configured andpositioned such that each lid structure is separated from each adjacentlid structure by a corresponding thermal break. A heat spreader assemblyis positioned in thermally conductive interface with the plurality oflid structures. The heat spreader assembly is configured to cover anaggregation of the plurality of lid structures. The heat spreaderassembly includes a plurality of separately defined heat transfermembers respectively configured and positioned to overlie the pluralityof lid structures. The heat spreader assembly is configured to limitheat transfer between different heat transfer members within the heatspreader assembly.

In an example embodiment, a method is disclosed for thermal managementof a multi-chip-module. The method includes positioning a first lidstructure over a temperature sensitive component within themulti-chip-module. The method also includes positioning a second lidstructure over a heat source within the multi-chip-module. The secondlid structure is separated from the first lid structure by a thermalbreak. The method also includes positioning a heat spreader assembly inthermally conductive interface with both the first lid structure and thesecond lid structure. The heat spreader assembly includes a first heattransfer member configured and positioned to overlie the first lidstructure. The heat spreader assembly includes a second heat transfermember configured and positioned to overlie the second lid structure.The heat spreader assembly is configured to limit heat transfer betweenthe first heat transfer member and the second heat transfer member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of an example multi-chip-module (MCM), inaccordance with some embodiments of the present invention.

FIG. 2 shows the example MCM of FIG. 1, with a Thermal InterfaceMaterial (TIM) disposed over the interposer device and over the variousdie disposed on the interposer device, in accordance with someembodiments of the present invention.

FIG. 3A shows the example MCM of FIG. 2, with lid structures positionedon the top surface of the stiffener structure to cover the interposerdevice, in accordance with some embodiments of the present invention.

FIG. 3B shows use of a single lid structure with a gap cut through acenter region of the single lid structure to form a thermal break, inaccordance with some embodiments of the present invention.

FIG. 4A shows a vertically exploded diagram of a heat spreader assemblyconfigured for positioning on the lid structures, in accordance withsome embodiments of the present invention.

FIG. 4B shows the heat spreader assembly of FIG. 4A in an assembledform, in accordance with some embodiments of the present invention.

FIG. 5A shows a vertically exploded diagram of a heat spreader assemblythat utilizes perforations to reduce lateral thermal conduction withinthe heat spreader assembly at the location of the thermal break, inaccordance with some embodiments of the present invention.

FIG. 5B shows the heat spreader assembly of FIG. 5A in an assembledform, in accordance with some embodiments of the present invention.

FIG. 6A shows a vertically exploded diagram of a heat spreader assemblythat includes a U-shaped heat transfer member and a rectangular heattransfer member, in accordance with some embodiments of the presentinvention.

FIG. 6B shows the heat spreader assembly of FIG. 6A in an assembledform, in accordance with some embodiments of the present invention.

FIG. 7 shows a vertically exploded diagram of the MCM of FIGS. 1 through4B, in conjunction with a thermoelectric cooler (TEC) and heat sinkstructures, in accordance with some embodiments of the presentinvention.

FIG. 8 shows the assembled MCM of FIG. 7, in accordance with someembodiments of the present invention.

FIG. 9A shows a diagram of a vertical cross-section through an exampleMCM, in accordance with some embodiments of the present invention.

FIG. 9B shows a diagram of a vertical cross-section through a variationof the example MCM of FIG. 9A, in which another heat spreader assemblyis used, in accordance with some embodiments of the present invention.

FIG. 9C shows a diagram of a vertical cross-section through a variationof the example MCM of FIG. 9A, in which another heat spreader assemblyis used, in accordance with some embodiments of the present invention.

FIG. 10 shows a flowchart of a method for thermal management of an MCM,in accordance with some embodiments of the present invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail in order not to unnecessarily obscure the presentinvention.

A Multi-Chip-Module (MCM) can be composed of heterogeneous components.For silicon photonic MCM's, these components can include III-V material,in addition to one or more CMOS (Complementary Metal-OxideSemiconductor) die. A III-V material is a semiconductor compoundcontaining elements from Group III (Boron, Aluminum, Gallium, Indium,Thallium) and Group V (Nitrogen, Phosphorous, Arsenic, Antimony,Bismuth) of the periodic table. In some applications, the TotalDissipated Power (TDP) within an MCM can exceed 200 Watts (W), resultingin semiconductor junction temperatures in excess of 90° Celsius (C), andsometimes over 100° C. While CMOS devices can nominally operate at thesetemperatures, the same cannot be said of III-V materials. For example,lasers (e.g., DFB (distributed feedback laser), DBR (distributed Braggreflector laser), FP (Fabry-Perot laser) and semiconductor opticalamplifiers (SOA) formed of III-V material will suffer significantreduction in both their wall plug efficiency and mean time to failure(MTTF) when operating at such high temperatures. Such adverseoperational behavior at high operating temperature can limit the utilityof heterogeneous MCM's.

Embodiments are disclosed herein for a thermal management system for anMCM that provides one or more thermal paths from one or more elevatedtemperature region(s) within the MCM to an ambient environment, i.e., toan environment outside the MCM. The thermal management system createsseparate thermal-transfer-environments for separate regions of the MCMor similar assembly of heterogeneous components. Eachthermal-transfer-environment can be referred to as a“micro-environment.” The thermal management system disclosed herein canalso be referred to as an Integrated Cooling Environment (ICE).

A design consideration and challenge for electronic packaging is heatspreading. For ideal heat sink behavior, a base of the electronicpackaging would have uniform temperature. However, semiconductor die actas non-uniform heat sources. In this situation, a heat spreader platescan be included within the thermal design to improve the thermalresistance. In some configurations, the base of the heat sink functionsas the heat spreader plate. In some configurations, vapor chambers andheat pipes can be used to improve heat spreading. For heterogeneousMCM's, heat spreading is also a concern. Embodiments of the thermalmanagement system disclosed herein function to increase heat spreadingwithin separate regions of the MCM, while retarding heat spreadingbetween those separate regions of the MCM.

There are three primary modes of heat transfer: conduction, convection,and radiation. For temperatures less than 100° C., radiation is usuallyneglected. Within the MCM package, convection can be neglected too.Therefore, the dominant mode for heat transfer within the MCM package isconduction. The thermal management system disclosed herein is acomposite structure that includes strategically placed “thermal breaks”to thermally isolate separate regions of the MCM.

FIG. 1 shows a diagram of an example MCM, in accordance with someembodiments of the present invention. The MCM includes an interposerdevice 1000. In various embodiments, the interposer device 1000 caninclude a number of optical waveguides and/or local metal routing and/orthrough-silicon vias (TSV's). In various embodiments, the interposerdevice 1000 can be formed of a silicon-based material, ceramic, glass,or of an organic composite material, among other materials. The MCM alsoincludes a silicon photonics die 1100. In some embodiments, the siliconphotonics die 1100 can include one or more CMOS device(s) as well aspassive and/or active photonic devices. In various embodiments, the MCMcan include one or more silicon photonics die 1100. Also, in variousembodiments, the MCM can include a plurality of silicon photonics die1100 and/or CMOS die on the interposer device 1000. The siliconphotonics die 1100 and/or CMOS die that are present on the interposerdevice 1000 are spatially separated from III-V material die present onthe interposer device 1000.

The MCM also includes a number of SOA's or other III-V material die1210, 1220. The SOA's and other III-V material die are more susceptibleto temperature-induced problems. Therefore, the SOA's and other III-Vmaterial die are spatially separated on the interposer device 1000 fromthe silicon photonics die 1100 and/or other CMOS die that may behave asheat sources. In some embodiments, the MCM can also include a laser die1230 (such as a distributed feedback (DFB) laser die, by way of example)and/or other III-V material die, that are more susceptible totemperature-induced problems. Again, the laser die 1230 and other III-Vmaterial die are spatially separated on the interposer device 1000 fromthe silicon photonics die 1100 and/or other CMOS die. Also, in someembodiments, the MCM includes an optical fiber-to-chip or opticalfiber-to-interposer assembly 1300. As shown in the example of FIG. 1, insome embodiments, the optical fiber-to-chip or opticalfiber-to-interposer assembly 1300 can be a 12 optical fiber MT(mechanical transfer) ferrule configured for connection to theinterposer device 1000. However, it should be understood that in otherembodiments, the optical fiber-to-chip or optical fiber-to-interposerassembly 1300 can be essentially any other type and/or configuration ofoptical data communication connection(s) to the interposer device 1000.Also, it should be understood that in various embodiments, a pluralityof optical fiber-to-chip assemblies and/or optical fiber-to-interposerassemblies can be implemented/utilized.

The MCM also includes a substrate device 1400 that serves to fanoutelectrical signal(s) while concurrently providing a power supply, e.g.,Vdd, Vss, etc., to devices of the MCM. In various embodiments, thesubstrate device 1400 can be fabricated from one or more of essentiallyany material used in electronic packages, such as epoxy compositestructures, ceramic, and/or glass, among other materials. The substratedevice 1400 can be configured to interface with one or more of a LandGrid Array (LGA), and/or a Ball Grid Array (BGA), and/or any othersubstrate electrical connection technology/scheme available in thesemiconductor device industry. Also, in some embodiments, if thesubstrate device 1400 has sufficient planarity and features, e.g.,electrical routing and optical routing, the substrate device 1400 can beconfigured to provide functionality equivalent to the interposer device1000. And, in some of these embodiments, and the interposer device 1000can be eliminated from the MCM.

The example MCM of FIG. 1 also includes a stiffener structure 1500. Insome embodiments, such as shown in the example of FIG. 1, the stiffenerstructure 1500 is “C-shaped.” In some embodiments, the C-shapedstiffener structure 1500 can be used when the substrate device 1400 doesnot allow for cavities, such as when the substrate device 1400 is formedin accordance with organic substrate technology. It should beunderstood, however, that in various embodiments in which cavities canbe formed within the substrate device 1400, the stiffener structure 1500can have a different shape that is not C-shaped. Also, in variousembodiments, the stiffener structure can have different thicknesses. Inthe example MCM of FIG. 1, the stiffener structure 1500 has a thicknesslarge enough to accommodate passage of thefiber-to-chip/fiber-to-interposer assembly 1300 through a layer(vertical layer) of the MCM where the stiffener structure 1500 resides.Also, in the example MCM of FIG. 1, the stiffener structure 1500 has athickness large enough to extend vertically (as measured in thethickness direction) beyond a vertical extent of various die disposed onthe interposer device 1000 (such as the silicon photonics/CMOS die 1100,the SOA/III-V material die 1210, 1220, and the laser/III-V material die1230), so that when a lid structure 1710, 1720 (see FIG. 3A) ispositioned on the top of the stiffener structure 1500, the lid structure1710, 1720 does not physically press into the various die disposed onthe interposer device 1000.

It should be understood that the example MCM of FIG. 1 is depicted in asimplified manner to avoid unnecessarily obscuring description of thepresent invention. In various embodiments, the example MCM of FIG. 1 caninclude adhesives and/or solder for attaching various components to eachother. Also, in various embodiments, standard electronic packagingtechniques can be used to assemble the MCM. For example, a CapillaryUnderfill (CUF) technique can be used to adhere the siliconphotonics/CMOS die 1100 to the interposer device 1000. FIG. 2 shows theexample MCM of FIG. 1, with a Thermal Interface Material (TIM) 1600disposed over the interposer device 1000 and over the various diedisposed on the interposer device 1000, such as over the siliconphotonics/CMOS die 1100, the SOA/III-V material die 1210, 1220, andlaser/III-V material die 1230, in accordance with some embodiments ofthe present invention. In some embodiments, the TIM 1600 is dispensedonto the MCM as a viscous/flowable material. As the lid structures 1710,1720 are attached to the MCM, e.g., are positioned on the top surface ofthe stiffener structure 1500 to cover the interposer device 1000, thelid structures 1710, 1720 displace the TIM 1600 and cause the TIM 1600to flow within a volume that is bounded by a combination of thestiffener structure 1500, the lid structures 1710, 1720, the interposerdevice 1000, and the substrate device 1400. It should be understood thatin various embodiments, the TIM 1600 does not need to fill the entirevolume that is bounded by the combination of the stiffener structure1500, the lid structures 1710, 1720, the interposer device 1000, and thesubstrate device 1400. In some embodiments, the TIM 1600 is disposed tojust occupy an interior space between and around the siliconphotonics/CMOS die 1100, the SOA/III-V material die 1210, 1220, and thelaser/III-V material die 1230, where the interior space is surrounded bythe stiffener structure 1500 and is vertically bounded by the interposerdevice 1000 and the lid structures 1710, 1720 that are positioned on topof the stiffener structure 1500.

In some embodiments, an underside of the lid structures 1710, 1720 caninclude various physical features that form corresponding physicalfeatures within the TIM 1600. For example, FIG. 2 shows a ridge feature201 that bisects the TIM 1600, and that is formed by placement of thelid structures 1710, 1720 on the stiffener structure 1500. In variousembodiments, the size, shape, and placement of the lid structures 1710,1720 can be defined to form essentially any necessary configuration ofphysical feature with the TIM 1600.

It should be understood that the configuration of the stiffenerstructure 1500 sets the thickness of the TIM 1600. Therefore, as thethickness of the stiffener structure 1500 increases, the thickness ofthe TIM 1600 increases. And, as the thickness of the stiffener structure1500 decreases, the thickness of the TIM 1600 decreases. As thethickness of the TIM 1600 decreases, the thermal resistance through theTIM 1600 decreases. Therefore, to increase heat transfer through the TIM1600, it is desirable to have a thinner stiffener structure 1500 and acorrespondingly thinner TIM 1600.

The TIM 1600 is a material that is contaminant-free and chemicallycompatible with the materials of the interposer device 1000 and thevarious die disposed on the interposer device 1000. The TIM 1600 alsohas a viscosity high enough so that the TIM 1600 will remain in placeduring the lifetime of the MCM. Also, the TIM 1600 is a material oflowest possible/available thermal resistance. For example, in someembodiments, a thermal conductivity of the TIM 1600 can be on the orderof magnitude of about 1 Watt per meter-Kelvin (W/m-K). By way ofcomparison to the low thermal conductivity of the TIM 1600 of about 1W/m-K, copper has a much higher thermal conductivity of about 385 W/m-K.Therefore, the TIM 1600 is considered a poor conductor of thermalenergy. In some embodiments, the lid structures 1710 and 1720 areseparated from each other by a distance of about 1 millimeter, and thevertical distance between the die disposed on the interposer device 1000and the lid structures 1710 and 1720 is less than about 50 micrometers.Therefore, the thickness of the vertical conductive path through the TIM1600 is orders of magnitude smaller than the lateral dimension of theTIM 1600. In some embodiments, the TIM 1600 can be COOL-GREASE® orCOOL-GEL® or COOL-SILVER™ or COOL-GAPFILL™ by AI Technology, Inc. Insome embodiments, the TIM 1600 can be Master Bond EP30TC by Master BondInc. In some embodiments, the TIM 1600 can be a metal or metal alloy,such as Indium (In), Indium-Lead (InPb), among other materials. Itshould be understood that in various embodiments, the TIM 1600 can beessentially any thermal interface material that is used in semiconductorpackaging to enhance thermal coupling between components, such asthermal grease, thermal adhesive, and/or thermal gap filler, amongothers.

FIG. 3A shows the example MCM of FIG. 2, with lid structures 1710 and1720 positioned on the top surface of the stiffener structure 1500 tocover the interposer device 1000 and cause the TIM 1600 to flow withinthe volume that is bounded by the stiffener structure 1500, the lidstructures 1710, 1720, the interposer device 1000, and the substratedevice 1400, in accordance with some embodiments of the presentinvention. In some embodiments, the lid structures 1710 and 1720 are twoseparate pieces and are physically separated from each other by a gap1730 so as to form a thermal break between the two lid structures 1710and 1720. In some embodiments, a lid configuration for placement on thestiffener structure 1500 can be a single lid structure or more than twolid structures. For example, FIG. 3B shows use of a single lid structure1740 with a gap 1742 cut through a center region of the single lidstructure 1740 to form a thermal break, in accordance with someembodiments of the present invention. In some embodiments, an amount ofthe TIM 1600 may flow into the gap 1730/1742 to form the ridge feature201 that bisects the TIM 1600, as previously described with regard toFIG. 2. In some embodiments, the gap 1730 can be filled with a solidmaterial, such as plastic or dielectric material, so that the lidstructures 1710 and 1720 and the material that fills the gap 1730collectively form a single unit structure. In some embodiments, the gap1742 can be filled with a solid material, such as plastic or dielectricmaterial, so that the lid structure 1740 and the material that fills thegap 1742 collectively form a single unit structure.

With reference to FIG. 3A, the lid structure 1710 is configured to coverthe region of the interposer device 1000 where the higher operatingtemperature silicon photonics/CMOS die 1100 are disposed. And, the lidstructure 1720 is configured to cover the region of the interposerdevice 1000 where the temperature sensitive SOA/III-V material die 1210,1220, and laser/III-V material die 1230 are disposed. In this manner,the heat transmitted into the lid structure 1710 from the higheroperating temperature silicon photonics/CMOS die 1100 does not readilyconduct to the lid structure 1720 and into the temperature sensitiveSOA/III-V material die 1210, 1220, and laser/III-V material die 1230. Invarious embodiments, the lid structures 1710 and 1720 are formed of ahigh thermal conductivity material, such as copper, or aluminum, orcopper alloy, or aluminum alloy, among others. In various embodiments,the lid structures 1710 and 1720 are formed of a material having athermal conductivity of at least 100 W/m-K.

A size 1732 of the gap 1730 corresponds to a minimum heat transferdimension across the gap 1730 between the lid structures 1710 and 1720.In various embodiments, the size 1732 of the gap 1730 as measuredperpendicularly between opposing surfaces of the lid structures 1710 and1720 is dependent upon a number of parameters, such as the TDP of thevarious die disposed on the interposer device 1000, the thermalresistance of the TIM 1600, and the thermal resistance to ambient.Similarly, a size 1744 of the gap 1742 corresponds to a minimum heattransfer dimension across the gap 1742 between a portion of the lidstructure 1740 overlying a heat source region and a portion of the lidstructure 1740 overlying a temperature-sensitive region. The size 1744of the gap 1742 is dependent upon a number of parameters, such as theTDP of the various die disposed on the interposer device 1000, thethermal resistance of the TIM 1600, and the thermal resistance toambient.

In some embodiments, the gap 1730/1742 can be kept empty, e.g., the TIM1600 can be kept out of the gap 1730. However, even if the TIM 1600flows into the gap 1730/1742, it should be understood that the poorthermal conductivity of the TIM 1600 still allows the gap 1730/1742 tofunction as a thermal break. And, the size 1732/1744 of the gap1730/1742 can be very small, even with TIM 1600 present within the gap1730/1742, with the gap 1730/1742 functioning as a thermal break. Morespecifically, because the thermal conductivity of the TIM 1600 is somuch less than the thermal conductivity of the lid structures 1710,1720, 1740 (e.g., copper, or aluminum, or copper alloy, or aluminumalloy, among others), even with TIM 1600 present in the gap 1730/1742,the size 1732/1744 of the gap 1730/1742 can be very small. In someembodiments, the size 1732/1744 of the gap 1730/1742 is about 1millimeter. In some embodiments, the size 1732/1744 of the gap 1730/1742is less than about 1 millimeter. In some embodiments, the size 1732/1744of the gap 1730/1742 is less than about 0.5 millimeter. In someembodiments, the size 1732/1744 of the gap 1730/1742 is less than about0.2 millimeter. Also, in some embodiments, the size 1732/1744 of the gap1730/1742 is greater than about 1 millimeter.

In various embodiments, a vertical thickness of the lid structures 1710,1720, 1740, is sufficient to provide for their structural integrity. Asmaller vertical thickness of the lid structures 1710, 1720, 1740 willreduce thermal resistance between heat sources underlying the lidstructures 1710, 1720, 1740, e.g., the various die disposed on theinterposer device 1000, and ambient. However, a larger verticalthickness of the lid structures 1710, 1720, 1740 can provide betterthermal spreading between the heat sources underlying the lid structures1710, 1720, 1740, e.g., the various die disposed on the interposerdevice 1000, and ambient. Therefore, the vertical thickness of the lidstructures 1710, 1720, 1740 can be set to provide a specified trade-offbetween thermal resistance and thermal spreading with regard to heattransfer from the heat sources underlying the lid structures 1710, 1720,1740, e.g., the various die disposed on the interposer device 1000, toambient. In some embodiments, the lid structures 1710, 1720, 1740 have avertical thickness of about 1 millimeter. In some embodiments, the lidstructures 1710, 1720, 1740 have a vertical thickness less than about 1millimeter. In some embodiments, the lid structures 1710, 1720, 1740have a vertical thickness more than about 1 millimeter.

FIG. 4A shows a vertically exploded diagram of a heat spreader assembly2000 configured for positioning on the lid structures 1710, 1720, 1740,in accordance with some embodiments of the present invention. FIG. 4Bshows the heat spreader assembly 2000 in an assembled form, inaccordance with some embodiments of the present invention. It should beunderstood that the heat spreader assembly 2000 is provided by way ofexample, and can be modified in various ways in various embodiments. Forexample, various features, dimensions, materials, etc., of the heatspreader assembly 2000 can change between different embodiments,depending on specific thermal and/or mechanical needs of the MCM. In theexample of FIGS. 4A-4B, the heat spreader assembly 2000 includes twoheat transfer members 2010 and 2020 positioned between a lower plate2040 and an upper plate 2050. Each of the heat transfer members 2010 and2020 is in thermal contact with each of the lower plate 2040 and theupper plate 2050. And, physical connections between each of the heattransfer members 2010 and 2020 and each of the lower plate 2040 and theupper plate 2050 serve to maintain physical positions of the heattransfer members 2010 and 2020 relative to each other and relative tothe lower plate 2040 and the upper plate 2050. It should be understoodthat in other embodiments, the heat spreader assembly 2000 can includemore than two heat transfer members, depending on how the heat sourcesand temperature-sensitive regions are distributed within the MCM, withthe objective being to transfer heat away from the heat sources withinthe MCM without adversely impacting the temperature-sensitive regionswithin the MCM.

The heat transfer member 2010 is configured to provide for high thermalconductivity between a portion of the lower plate 2040 in contact withthe heat transfer member 2010 and a portion of the upper plate 2050 incontact with the heat transfer member 2010. And, the heat transfermember 2020 is configured to provide for high thermal conductivitybetween a portion of the lower plate 2040 in contact with the heattransfer member 2020 and a portion of the upper plate 2050 in contactwith the heat transfer member 2020. Also, in the example embodiment ofFIGS. 4A-4B, a bottom surface of the lower plate 2040 provides a planarsurface for good thermal contact with and connection to the lidstructures 1710, 1720, 1740.

The vertical thicknesses of the lower plate 2040 and the upper plate2050 can be set to provide a specified trade-off between thermalresistance and thermal spreading with regard to heat transfer from theheat sources within the MCM to ambient. In some embodiments, the lowerplate 2040 can have a vertical thickness of about 1 millimeter. In someembodiments, the lower plate 2040 can have a vertical thickness of lessthan about 1 millimeter. In some embodiments, the lower plate 2040 canhave a vertical thickness of more than about 1 millimeter. In someembodiments, the upper plate 2050 can have a vertical thickness of about1 millimeter. In some embodiments, the upper plate 2050 can have avertical thickness of less than about 1 millimeter. In some embodiments,the upper plate 2050 can have a vertical thickness of more than about 1millimeter. In some embodiments, it can be desirable to have a thinneroverall stack thickness of the lower plate 2040, the heat transfermembers 2010/2020, and the upper plate 2050. In some embodiments, toachieve the thinner overall stack thickness, the thickness of one orboth of the lower plate 2040 and the upper plate 2050 is reduced whilemaintaining a nominal or larger thickness of the heat transfer members2010/2020.

In some embodiments, each of the heat transfer members 2010 and 2020 isformed of a solid material, such as solid copper, or solid aluminum, orsolid copper alloy, or solid aluminum alloy, or another material havinghigh thermal conductivity. In some embodiments, each of the heattransfer members 2010 and 2020 is formed as a vapor chamber. Forexample, in some embodiments, each of the heat transfer members 2010 and2020 can be formed as a vapor chamber that includes a sealed vacuumvessel having an internal wicking structure and an internal workingfluid that is in equilibrium with its own vapor. In some embodiments,the sealed vacuum vessel is formed of copper and the internal wickingstructure is formed of sintered copper powder on the interior walls ofthe vacuum vessel. In some embodiments, the working fluid is de-ionizedwater. It should be understood, however, that in various embodiments,the sealed vacuum vessel, internal wicking structure, and working fluidcan be formed of essentially any materials that enable the vapor chamberto function as a suitable heat transfer acceleration device. In someembodiments, the working fluid inside of the vapor chamber vaporizesnear a surface of the vapor chamber where heat is applied and condensesat a sufficiently cooler surface of the vapor chamber, with the workingfluid recirculating by way of the internal wicking structure. Thevaporization of the working fluid serves to spread heat within the vaporchamber and quickly move the heat to the cooler surface of the vaporchamber. In some embodiments, the heat transfer members 2010 and 2020are formed as vapor chambers that have an effective thermal conductivitythat is 5 to 100 times larger than the thermal conductivity of solidcopper. In some embodiments, use of vapor chambers for the heat transfermembers 2010 and 2020 can provide for improved thermal spreading, ascompared to use of a solid material for the heat transfer members 2010and 2020. The improved thermal spreading provided by configuring theheat transfer members 2010 and 2020 as vapor chambers in turn improvesthe efficiency of the heat spreader assembly 2000, thereby lowering theoverall thermal resistance from the heat sources within the MCM toambient.

Also, in some embodiments, either of the heat transfer members 2010 and2020 can be formed as a heat spreader plate having integrated heatpipes. In some embodiments, a heat pipe in this context is a sealedcopper tube having an interior that includes a working fluid under avacuum pressure. The heat pipe also includes an internal wickingstructure. In this manner, the heat pipe is quite similar to the vaporchamber described above in both structure and function, with the heatpipe configured to provide for a more directional transfer of heat. Theheat pipes can be positioned in thermal contact with the heat spreaderplate to provide for transfer of heat away from the heat spreader plate.

In the example heat spreader assembly 2000, the heat transfer members2010 and 2020 are separated by a thermal break 2030 to limit thermalconduction between the heat transfer members 2010 and 2020. In someembodiments, the thermal break 2030 is formed as an air gap. It shouldbe understood that if the heat spreader assembly 2000 includes more thanthe two heat transfer members 2010 and 2020, adjacently positionedportions of heat transfer members can be separated from each other by acorresponding thermal break similar to the thermal break 2030. In someembodiments, the lower plate 2040 and the upper plate 2050 are uniformand contiguous, such as shown in FIGS. 4A-4B. In some embodiments, oneor both of the lower plate 2040 and the upper plate 2050 can bebifurcated to improve the thermal separation between the two heattransfer members 2010 and 2020. In some embodiments, the lower plate2040 that is connected to the lid structures 1710 and 1720 is bifurcatedin a manner to mirror a physical separation between the lid structures1710 and 1720. In some embodiments, the lower plate 2040 is omitted fromthe heat spreader assembly 2000, with the two heat transfer members 2010and 2020 configured for direct physical connection with the lidstructures 1710 and 1720, respectively.

In some embodiments, the lower plate 2040 and the upper plate 2050 mayallow for undesired heat transfer between the heat sources within theMCM (e.g., the higher operating temperature silicon photonics/CMOS die1100) and the temperature sensitive devices within the MCM (e.g.,SOA/III-V material die 1210, 1220, and laser/III-V material die 1230).In these embodiments, the lower plate 2040 can be perforated along theboundaries of the two heat transfer members 2010 and 2020 to decreaselateral thermal conduction within the lower plate 2040, and/or the upperplate 2050 can be perforated along the boundaries of the two heattransfer members 2010 and 2020 to decrease lateral thermal conductionwithin the upper plate 2050, while maintaining overall physicalplanarity of the heat spreader assembly 2000.

FIG. 5A shows a vertically exploded diagram of a heat spreader assembly2000A that utilizes perforations to reduce lateral thermal conductionwithin the heat spreader assembly 2000A at the location of the thermalbreak 2030, in accordance with some embodiments of the presentinvention. FIG. 5B shows the heat spreader assembly 2000A in anassembled form, in accordance with some embodiments of the presentinvention. The heat spreader assembly 2000A includes a lower plate 2040Ahaving perforations 2070 along the inner boundaries of the two heattransfer members 2010 and 2020. Similarly, heat spreader assembly 2000Aincludes an upper plate 2050A having perforations 2072 along the innerboundaries of the two heat transfer members 2010 and 2020. Theperforations 2070 reduce lateral thermal conduction within the lowerplate 2040A at the location of the thermal break 2030. And, theperforations 2072 reduce lateral thermal conduction within the upperplate 2050A at the location of the thermal break 2030.

In some embodiments, such as in the example heat spreader assembly 2000of FIGS. 4A-4B, the heat transfer members 2010 and 2020 have asubstantially symmetric shape and are of substantially equal shape andsize. However, in some embodiments, different heat transfer members(e.g., 2010, 2020) within the heat spreader assembly 2000 can havedifferent sizes and different shapes as needed to assist with limitingthermal communication (heat transfer) between the between the heatsources within the MCM (e.g., the higher operating temperature siliconphotonics/CMOS die 1100) and the temperature sensitive devices withinthe MCM (e.g., SOA/III-V material die 1210, 1220, and laser/III-Vmaterial die 1230). It should be understood that in various embodiments,the heat spreader assembly 2000 can include as many heat transfermembers (e.g., 2010, 2020) of whatever shape and size is necessary tosatisfy the thermal requirements of the MCM.

For example, FIG. 6A shows a vertically exploded diagram of a heatspreader assembly 2000B that includes a U-shaped heat transfer member2080 and a rectangular heat transfer member 2086, with the heat transfermember 2080 wrapping around the heat transfer member 2086, in accordancewith some embodiments of the present invention. FIG. 6B shows the heatspreader assembly 2000B in an assembled form, in accordance with someembodiments of the present invention. In the example heat spreaderassembly 2000B, the U-shaped heat transfer member 2080 and therectangular heat transfer member 2086 are separated from each other by athermal break 2088. In some embodiments, the thermal break 2088 isformed by an air gap. The example heat spreader assembly 2000B includesthe lower plate 2040 and the upper plate 2050. In some embodiments, thelower plate 2040 and/or the upper plate 2050 in the heat spreaderassembly 2000B can include perforations along the thermal break 2088, ina manner similar to the perforations 2070, 2072 described with regard toFIGS. 5A and 5B.

FIG. 7 shows a vertically exploded diagram of the MCM of FIGS. 1 through4B, in conjunction with a thermoelectric cooler (TEC) 3000 and heatsinks 4010 and 4020, in accordance with some embodiments of the presentinvention. It should be understood that the MCM arrangement of FIG. 7 isbased on a symmetric, bifurcated design, in which the lid structures1710, 1720 and heat spreader assembly 2000 are arranged with thermalbreaks so as to form two separate thermal control regions, such thatheat transfer from the MCM to ambient is controllable in a bifurcatedmanner. In other embodiments, the MCM arrangement may be non-symmetricand/or include more than two separate thermal control regions, i.e., maybe more than a bifurcated design. The TEC 3000 enables the user toeffectively reduce the thermal resistance from a given region of the MCMto ambient. In the example of FIG. 7, the TEC 3000 is placed to increaseheat transfer from the region of the MCM that has the temperaturesensitive die (SOA/III-V material die 1210, 1220, and laser/III-Vmaterial die 1230 disposed on the interposer device 1000) to ambient. Invarious embodiments, the MCM can include a plurality of TEC's 3000. Forexample, in some embodiments, the MCM can include one or more TEC 3000placed to affect heat transfer from all the die disposed on theinterposer device 1000. In some embodiments, the TEC 3000 is configuredto operate in accordance with the Peltier effect which creates atemperature difference by transferring heat between two electricaljunctions through which an electrical current is made to flow, such thatheat is removed at one electrical junction and deposited at the otherelectrical junction.

The heat sinks 4010 and 4020 are provided to dissipate heat to ambient.The example embodiment of FIG. 7 includes passive heat sinks 4010 and4020. However, in various embodiments, the heat sinks 4010 and 4020 canbe forced air heat sinks, and/or heat sinks with heat pipes, and/orvapor chambers, and/or water-cooled chill plates, and/or other types ofheat sinks. Also, the example embodiment of FIG. 7 shows the heat sinks4010 and 4020 as fin heat sinks. However, in other embodiments, the heatsinks 4010 and 4020 can be configured to include a pin array, foldedfins, skived fins, or other configurations. In the example embodiment ofFIG. 7, a vertical extent of the heat sink 4010 is less than a verticalextent of the heat sink 4020 to accommodate the vertical extent of theTEC 3000 and maintain a uniform overall vertical extent of the MCM.However, in some embodiments, the vertical extent of the MCM can varyover the footprint of the MCM.

FIG. 8 shows the assembled MCM of FIG. 7, in accordance with someembodiments of the present invention. Because the heat sinks 4010 and4020 are parallel fin heat sinks, there is a preferred direction ofairflow through the heat sinks 4010 and 4020. Specifically, thepreferred direction of air flow through the heat sinks 4010 and 4020 isparallel to the fins. In the example of FIG. 8, the preferred directionof airflow through the heat sinks 4010 and 4020 is set so that thetemperature sensitive die (SOA/III-V material die 1210, 1220, andlaser/III-V material die 1230 disposed on the interposer device 1000)are positioned upstream from the heat generating die (siliconphotonics/CMOS die 1100) disposed on the interposer device 1000,relative to a direction of air flow through the fins of the heat sinks4010, 4020, so that the temperature sensitive die will have improvedthermal performance. Specifically, because the heat sink 4010 associatedwith the temperature sensitive die is positioned upstream of the heatsink 4020 associated with the heat generating die, the heat sink 4010 isexposed to airflow of cooler temperature, thereby improving heattransfer from the fins of the heat sink 4010 to the air.

It should be understood that the physically/thermally separated lids1710, 1720 and the bifurcated heat spreader assembly 2000 form parts ofthe thermal management system disclosed herein which functions toincrease heat spreading within separate regions of the MCM, whileretarding heat spreading between those separate regions of the MCM.Strategically placed thermal breaks between the separate lids 1710 and1720 and within the heat spreader assembly 2000 serve to thermallyisolate separate regions of the MCM so that temperature sensitive diewithin the MCM can be thermally shielded from heat generating die withinthe MCM.

FIG. 9A shows a diagram of a vertical cross-section through an exampleMCM, in accordance with some embodiments of the present invention. Theinterposer 1000 is disposed on the substrate 1400. The stiffenerstructure 1500 is also disposed on the substrate 1400. The stiffenerstructure 1500 is configured to wrap around the interposer 1000. Anumber of temperature-sensitive devices 1210, 1220, 1230 are disposed onthe interposer 1000. A number of heat sources 1100 are disposed on theinterposer 1000. In some embodiments, the temperature-sensitive devices1210, 1220, 1230 are disposed together in a first region on theinterposer 1000, and the heat sources 1100 are disposed together in asecond region on the interposer 1000, with the first and second regionsthermally separated from each other to an extent possible. The opticalfiber-to-chip or optical fiber-to-interposer assembly 1300 is configuredand positioned to interface with photonics devices within thetemperature-sensitive devices 1210, 1220, 1230. In some embodiments, theTIM material 1600 is disposed around and over the interposer 1000 andaround and over the temperature-sensitive devices 1210, 1220, 1230 andaround and over the heat sources 1100.

The lid structures 1710 and 1720 are positioned on the stiffenerstructure 1500 to extend over the interposer 1000. The lid structure1710 is configured and positioned to extend over the heat sources 1100within the MCM. The lid structure 1720 is configured and positioned toextend over the temperature sensitive devices 1210, 1220, 1230 withinthe MCM. The lid structure 1710 and the lid structure 1720 are alsoconfigured and positioned such that a thermal break 901 separatesadjacent portions of the lid structures 1710 and 1720 from each other.The thermal break 901 is configured to limit transfer of heat emanatingfrom the heat sources 1100 to the temperature sensitive devices 1210,1220, 1230, by way of the lid structures 1710 and 1720. In someembodiments, the thermal break 901 is configured as the gap 1730 and theTIM 1600 is disposed on the interposer 1000 so that when the lidstructures 1710 and 1720 are positioned on the stiffener structure 1500,an amount of the TIM 1600 flows into the gap 1730 between the lidstructures 1710 and 1720. In some embodiments, the thermal break 901 isformed as an air gap. However, in other embodiments, the thermal break901 can be formed by a solid material, such as a plastic material ordielectric material, among other materials of low thermal conductivity.The size 1732 of the thermal break 901 corresponds to a minimum heattransfer dimension across the thermal gap 901 between the lid structures1710 and 1720. In some embodiments, the minimum heat transfer dimensionacross the thermal gap 901 is greater than zero and less than or equalto about 1 millimeter as measured between the two adjacent lidstructures 1710 and 1720.

The heat spreader assembly 2000 is positioned in thermally conductiveinterface with the lid structures 1710 and 1720. It should be understoodthat thermally conductive interface, as used herein with regardpositioning of a first structure in thermally conductive interface witha second structure, can refer to a particular surface of the firststructure being in either partial or complete physical contact with aparticular surface of the second structure, and/or can refer to disposalof a thermally conductive bonding material between a particular surfaceof the first structure and a particular surface of the second structure.In the example of FIG. 9A, the heat spreader assembly 2000 includes thelower plate 2040 and the upper plate 2050. The heat spreader assembly2000 also includes the heat transfer members 2010 and 2020 positionedbetween the lower plate 2040 and the upper plate 2050 and in thermallyconductive interface with the lower plate 2040 an the upper plate 2050.The heat transfer members 2010 and 2020 are separated from each other bythe thermal break 2030. In some embodiments, the thermal break 2030 isformed as an air gap. However, in other embodiments, the thermal break2030 can be formed by a solid material, such as a plastic material ordielectric material, among other materials of low thermal conductivity.The heat transfer member 2010 is configured to promote transfer ofthermal energy from the lid structure 1720 toward the ambientenvironment outside of the MCM. The heat transfer member 2020 isconfigured to promote transfer of thermal energy from the lid structure1710 toward the ambient environment outside of the MCM. Also, in someembodiments, the lower plate 2040 and the upper plate 2050 areconfigured to maintain a spatial relationship between the heat transfermembers 2010 and 2020, while limiting thermal communication between theheat transfer members 2010 and 2020. In the example of FIG. 9A, thelower plate 2040 vertically bounds the thermal break 2030 within theheat spreader assembly 2000. Also, in the example of FIG. 9A, the upperplate 2050 vertically bounds the thermal break 2030 within the heatspreader assembly 2000. In the example of FIG. 9A, the TEC 3000 ispositioned in thermally conductive interface with the heat spreaderassembly 2000 at a location above the heat transfer member 2010. The TEC3000 is configured to promote transfer of thermal energy from the heattransfer member 2010 toward the ambient environment outside of the MCM.It should be understood that the TEC 3000 provides for improved coolingof the region below the lid structure 1720 where thetemperature-sensitive devices 1210, 1220, 1230 are located.

The heat sink structure 4010 is positioned in thermally conductiveinterface with the TEC 3000. The heat sink structure 4020 is positionedin thermally conductive interface with the heat spreader assembly 2000.More specifically, the heat sink structure 4020 is positioned above theheat transfer member 2020 to promote transfer of thermal energy from theheat transfer member 2020 toward the ambient environment outside of theMCM. In some embodiments, the fin structures of the heat sink structure4010 and the fin structures of the heat sink structure 4020 are orientedso that air can be flowed between the fin structures in a direction 903moving from the heat sink structure 4010 toward and through the heatsink structure 4020. In this manner, cooler air flows through the heatsink structure 4010 that is positioned in the heat transfer path awayfrom the temperature-sensitive devices 1210, 1220, 1230, therebyimproving the efficiency of heat transfer away from thetemperature-sensitive devices 1210, 1220, 1230.

FIG. 9B shows a diagram of a vertical cross-section through a variationof the example MCM of FIG. 9A, in which another heat spreader assembly2000C is used, in accordance with some embodiments of the presentinvention. In the heat spreader assembly 2000C, the lower plate 2040 ofthe heat spreader assembly 2000C is either perforated along the thermalbreak 2030 or not present along the thermal break 2030. In someembodiments, the heat spreader assembly 2000C is configured andpositioned such that the thermal break 901 between the lid structures1710 and 1720 is contiguous with the thermal break 2030 between the heattransfer members 2010 and 2020. The configuration of the lower plate2040 in the heat spreader assembly 2000C can improve thermal separationbetween the lid structure 1710 and the lid structure 1720. Also, in someembodiments, the upper plate 2050 in the heat spreader assembly 2000Ccan function to maintain a spatial relationship between the heattransfer member 2010 and the heat transfer member 2020. In someembodiments, the lower plate 2040 in the heat spreader assembly 2000C isformed as a contiguous structure at locations outside of the footprintof the interposer 1000, such as at locations that overlie the stiffenerstructure 1500.

FIG. 9C shows a diagram of a vertical cross-section through a variationof the example MCM of FIG. 9A, in which another heat spreader assembly2000D is used, in accordance with some embodiments of the presentinvention. The heat spreader assembly 2000D does not include the lowerplate 2040 that is present in the heat spreader assembly 2000. The heatspreader assembly 2000D is configured and positioned such that the heattransfer member 2010 is in thermally conductive interface with the lidstructure 1720, and the heat transfer member 2020 is in thermallyconductive interface with the lid structure 1710. In this manner, thethermal break 2030 is contiguous with the thermal break 901. The upperplate 2050 in the heat spreader assembly 2000D functions to maintain aspatial relationship between the heat transfer member 2010 and the heattransfer member 2020.

It should be understood that a thermal management system for amulti-chip-module (MCM) is disclosed herein. The thermal managementsystem can include a plurality of lid structures (e.g., 1710, 1720)including at least one lid structure (e.g., 1710) configured to overlieone or more heat sources (e.g., 1100) within the MCM and at least onelid structure (e.g., 1720) configured to overlie one or more temperaturesensitive components (e.g., 1210, 1220, 1230) within the MCM. Theplurality of lid structures are configured and positioned such that eachlid structure is separated from each adjacent lid structure by acorresponding thermal break (e.g., 901). A heat spreader assembly (e.g.,2000, 2000A, 2000B, 2000C, 2000D) is positioned in thermally conductiveinterface with the plurality of lid structures. The heat spreaderassembly is configured to cover an aggregation of the plurality of lidstructures. The heat spreader assembly includes a plurality ofseparately defined heat transfer members (e.g., 2010, 2020) respectivelyconfigured and positioned to overlie the plurality of lid structures.The heat spreader assembly is configured to limit heat transfer betweendifferent heat transfer members within the heat spreader assembly, suchas by way of a thermal break (e.g., 2030).

In some embodiments, each of the plurality of lid structures (e.g.,1710, 1720) is formed of a material having a thermal conductivity of atleast 100 Watts per meter-Kelvin (W/m-K). In some embodiments, each ofthe plurality of lid structures (e.g., 1710, 1720) is formed of copper,or aluminum, or copper alloy, or aluminum alloy. In some embodiments,each thermal break (e.g., 901) that separates any two adjacent ones ofthe plurality of lid structures (e.g., 1710, 1720) has a minimum heattransfer dimension (e.g., 1732) greater than zero and less than or equalto about 1 millimeter as measured between the two adjacent ones of theplurality of lid structures. In some embodiments, a vertical thicknessof each of the plurality of lid structures (e.g., 1710, 1720) is greaterthan zero and less than or equal to about 1 millimeter.

In some embodiments, the one or more heat sources (e.g., 1100) withinthe multi-chip-module include at least one silicon photonics die or atleast one CMOS die. In some embodiments, the one or more temperaturesensitive components (e.g., 1210, 1220, 1230) include at least one III-Vmaterial die. In some embodiments, each of the plurality of lidstructures (e.g., 1710, 1720) is configured to interface with astiffener structure (e.g., 1500) of the MCM. In some embodiments, atleast one thermal break (e.g., 901) that separates two adjacent ones ofthe plurality of lid structures (e.g., 1710, 1720) is formed as a regionof thermal interface material (e.g., 1600) flowed into the regionbetween the two adjacent ones of the plurality of lid structures duringplacement of the two adjacent ones of the plurality of lid structures onthe MCM. In some embodiments, at least one thermal break (e.g., 901)that separates two adjacent ones of the plurality of lid structures(e.g., 1710, 1720) is formed as a region of air. In some embodiments, atleast one thermal break (e.g., 901) that separates two adjacent ones ofthe plurality of lid structures (e.g., 1710, 1720) is formed as a solidmaterial. In some embodiments, the plurality of lid structures (e.g.,1710, 1720) and any thermal break (e.g., 901) that separates twoadjacent ones of the plurality of lid structures are collectively formedas a single unit structure.

In some embodiments, the plurality of lid structures (e.g., 1710, 1720)have substantially co-planar top surfaces. In some embodiments, the heatspreader assembly (e.g., 2000, 2000A, 2000C) includes a lower plate(e.g., 2040) and an upper plate (e.g., 2050), with the plurality ofseparately defined heat transfer members (e.g., 2010, 2020) disposedbetween the lower plate (e.g., 2040) and the upper plate (e.g., 2050),and with the lower plate (e.g., 2040) positioned in thermally conductiveinterface with the substantially co-planar top surfaces of the pluralityof lid structures (e.g., 1710, 1720). In some embodiments, each of theplurality of separately defined heat transfer members (e.g., 2010, 2020)has a physical connection to at least one of the lower plate (e.g.,2040) and upper plate (e.g., 2050). In some embodiments, the lower plate(e.g., 2040) and upper plate (e.g., 2050) maintain physical positions ofthe plurality of separately defined heat transfer members (e.g., 2010,2020) relative to each other.

In some embodiments, each heat transfer member of the plurality ofseparately defined heat transfer members (e.g., 2010, 2020) is separatedfrom each adjacent heat transfer member of the plurality of separatelydefined heat transfer members by a corresponding thermal break (e.g.,2030). In some embodiments, each thermal break (e.g., 2030) between anytwo heat transfer members of the plurality of separately defined heattransfer members (e.g., 2010, 2020) is vertical bounded by at least oneof the lower plate (e.g., 2040) and the upper plate (e.g., 2050). Insome embodiments, at least one thermal break (e.g., 2030) between anytwo heat transfer members of the plurality of separately defined heattransfer members (e.g., 2010, 2020) is formed as a region of air. Insome embodiments, at least one thermal break (e.g., 2030) between anytwo heat transfer members of the plurality of separately defined heattransfer members (e.g., 2010, 2020) is formed as a solid material. Insome embodiments, at least one of the lower plate (e.g., 2040) and theupper plate (e.g., 2050) is perforated along at least one thermal break(e.g., 2030) located between adjacent heat transfer members (e.g., 2010,2020) within the heat spreader assembly (e.g., 2000A, 2000C).

In some embodiments, the lower plate (e.g., 2040) has a verticalthickness of less than or equal to about 1 millimeter, and the upperplate (e.g., 2050) has a vertical thickness of less than or equal toabout 1 millimeter. In some embodiments, at least one of the pluralityof separately defined heat transfer members (e.g., 2010, 2020) is formedas a solid material having a thermal conductivity of at least 200 W/m-K.In some embodiments, at least one of the plurality of separately definedheat transfer members (e.g., 2010, 2020) is formed as a vapor chamber.In some embodiments, at least one of the plurality of separately definedheat transfer members (e.g., 2010, 2020) is formed as a heat spreaderplate with integrated heat pipes.

In some embodiments, the thermal management system includes athermoelectric cooler (e.g., 3000) is positioned in thermally conductiveinterface with the heat spreader assembly (e.g., 2000, 2000A, 2000B,2000C, 2000D). The thermoelectric cooler (e.g., 3000) is configured tooverlie at least one heat transfer member (e.g., 2010) within the heatspreader assembly (e.g., 2000, 2000A, 2000B, 2000C, 2000D) that ispositioned to overlie at least one lid structure (e.g., 1720) of theplurality of lid structures (e.g., 1710, 1720) that is positioned tooverlie one or more temperature sensitive components (e.g., 1210, 1220,1230) within the MCM. In some embodiments, the thermal management systemincludes a plurality of heat sink structures (e.g., 4010, 4020)corresponding to the plurality of heat transfer members (e.g., 2010,2020) within the heat spreader assembly (e.g., 2000, 2000A, 2000B,2000C, 2000D). In some embodiments, the plurality of heat sinkstructures (e.g., 4010, 4020) are positioned to respectively overlie theplurality of heat transfer members (e.g., 2010, 2020) within the heatspreader assembly (e.g., 2000, 2000A, 2000B, 2000C, 2000D). Each of theplurality of heat sink structures (e.g., 4010, 4020) is in thermallyconductive interface with either the heat spreader assembly (e.g., 2000,2000A, 2000B, 2000C, 2000D) or the thermoelectric cooler (e.g., 3000).In some embodiments, the plurality of heat sink structures (e.g., 4010,4020) are configured and positioned physically separate from each other.In some embodiments, each of the plurality of heat sink structures(e.g., 4010, 4020) is configured to have fin structures of substantiallyparallel orientation.

FIG. 10 shows a flowchart of a method for thermal management of amulti-chip-module (MCM), in accordance with some embodiments of thepresent invention. The method includes an operation 5001 for positioninga first lid structure (e.g., 1720) over a temperature sensitivecomponent (e.g., 1210, 1220, 1230) within the MCM. In some embodiments,the temperature sensitive component (e.g., 1210, 1220, 1230) includes atleast one III-V material die. The method also includes an operation 5003for positioning a second lid structure (e.g., 1710) over a heat source(e.g., 1100) within the MCM, such that the second lid structure (e.g.,1710) is separated from the first lid structure (e.g., 1720) by athermal break (e.g., 901). In some embodiments, the heat source (e.g.,1100) within the MCM includes at least one silicon photonics die or atleast one CMOS die. In some embodiments, the first lid structure (e.g.,1720) and the second lid structure (e.g., 1710) are positioned inphysical contact with a stiffener structure (e.g., 1500) of the MCM. Insome embodiments, the first lid structure (e.g., 1720) and the secondlid structure (e.g., 1710) are positioned over a thermal interfacematerial (e.g., 1600), such that the thermal interface material (e.g.,1600) flows into the thermal break (e.g., 901) between the first lidstructure (e.g., 1720) and the second lid structure (e.g., 1710). Insome embodiments, the thermal break (e.g., 901) between the first lidstructure (e.g., 1720) and the second lid structure (e.g., 1710) isformed as a region of air. In some embodiments, the thermal break (e.g.,901) between the first lid structure (e.g., 1720) and the second lidstructure (e.g., 1710) is formed as a solid material.

The method also includes an operation 5005 for positioning a heatspreader assembly (e.g., 2000, 2000A, 2000B, 2000C, 2000D) in thermallyconductive interface with both the first lid structure (e.g., 1720) andthe second lid structure (e.g., 1710). The heat spreader assembly (e.g.,2000, 2000A, 2000B, 2000C, 2000D) includes a first heat transfer member(e.g., 2010) configured and positioned to overlie the first lidstructure (e.g., 1720). The heat spreader assembly (e.g., 2000, 2000A,2000B, 2000C, 2000D) also includes a second heat transfer member (e.g.,2020) configured and positioned to overlie the second lid structure(e.g., 1710). The heat spreader assembly (e.g., 2000, 2000A, 2000B,2000C, 2000D) is configured to limit heat transfer between the firstheat transfer member (e.g., 2010) and the second heat transfer member(e.g., 2020).

In some embodiments, the heat spreader assembly (e.g., 2000, 2000A,2000B, 2000C) includes a lower plate (e.g., 2040) and an upper plate(e.g., 2050), with the first heat transfer member (e.g., 2010) and thesecond heat transfer member (e.g., 2020) disposed between the lowerplate (e.g., 2040) and the upper plate (e.g., 2050), and with the lowerplate (e.g., 2040) in thermally conductive interface with the first lidstructure (e.g., 1720) and the second lid structure (e.g., 1710). Insome embodiments, the first heat transfer member (e.g., 2010) and thesecond heat transfer member (e.g., 2020) are separated from each otherby a thermal break (e.g., 2030). In some embodiments, the thermal break(e.g., 2030) between the first heat transfer member (e.g., 2010) and thesecond heat transfer member (e.g., 2020) is vertically bounded by atleast one of the lower plate (e.g., 2040) and the upper plate (e.g.,2050). In some embodiments, the thermal break (e.g., 2030) between thefirst heat transfer member (e.g., 2010) and the second heat transfermember (e.g., 2020) is formed as a region of air. In some embodiments,the thermal break (e.g., 2030) between the first heat transfer member(e.g., 2010) and the second heat transfer member (e.g., 2020) is formedas a solid material. In some embodiments, the lower plate (e.g., 2040)is perforated along the thermal break (e.g., 2030) between the firstheat transfer member (e.g., 2010) and the second heat transfer member(e.g., 2020). In some embodiments, the upper plate (e.g., 2050) isperforated along the thermal break (e.g., 2030) between the first heattransfer member (e.g., 2010) and the second heat transfer member (e.g.,2020). In some embodiments, the lower plate (e.g., 2040) is perforatedalong the thermal break (e.g., 2030) between the first heat transfermember (e.g., 2010) and the second heat transfer member (e.g., 2020),and the upper plate (e.g., 2050) is perforated along the thermal break(e.g., 2030) between the first heat transfer member (e.g., 2010) and thesecond heat transfer member (e.g., 2020).

In some embodiments, the method includes an optional operation 5007 forpositioning a thermoelectric cooler (e.g., 3000) in thermally conductiveinterface with the heat spreader assembly (e.g., 2000, 2000A, 2000B,2000C, 2000D). The thermoelectric cooler (e.g., 3000) is configured andpositioned to overlie the first heat transfer member (e.g., 2010) withinthe heat spreader assembly (e.g., 2000, 2000A, 2000B, 2000C, 2000D) thatis positioned to overlie the first lid structure (e.g., 1720) that ispositioned to overlie the temperature sensitive component (e.g., 1210,1220, 1230) within the MCM.

In some embodiments, the method includes an optional operation 5009 forpositioning a first heat sink structure (e.g., 4010) in thermallyconductive interface with the thermoelectric cooler (e.g., 3000). Insome embodiments, the method includes an optional operation 5011 forpositioning a second heat sink structure (e.g., 4020) in thermallyconductive interface with the heat spreader assembly (e.g., 2000, 2000A,2000B, 2000C, 2000D). The second heat sink structure (e.g., 4020) isconfigured and positioned to overlie the second heat transfer member(e.g., 2020) within the heat spreader assembly (e.g., 2000, 2000A,2000B, 2000C, 2000D) that is positioned to overlie the second lidstructure (e.g., 1710) that is positioned to overlie the heat sources(e.g., 1100) within the MCM. In some embodiments, the first heat sinkstructure (e.g., 4010) and the second heat sink structure (e.g., 4020)are configured and positioned physically separate from each other. Insome embodiments, each of the first heat sink structure (e.g., 4010) andthe second heat sink structure (e.g., 4020) is configured to have finstructures of substantially parallel orientation. In some embodiments,the method includes an optional operation 5013 for flowing air throughthe fin structures of the first heat sink structure (e.g., 4010) andthen through the fin structures of the second heat sink structure (e.g.,4020).

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications can be practiced. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive,and the invention is not to be limited to the details given herein, butmay be modified within the scope and equivalents of the describedembodiments.

What is claimed is:
 1. A thermal management system for amulti-chip-module, comprising: a plurality of lid structures includingat least one lid structure configured to overlie one or more heatsources within the multi-chip-module and at least one lid structureconfigured to overlie one or more temperature sensitive componentswithin the multi-chip-module, the plurality of lid structures configuredand positioned such that each lid structure is separated from eachadjacent lid structure by a corresponding thermal break; and a heatspreader assembly positioned in thermally conductive interface with theplurality of lid structures, the heat spreader assembly configured tocover an aggregation of the plurality of lid structures, the heatspreader assembly including a plurality of separately defined heattransfer members respectively configured and positioned to overlie theplurality of lid structures, the heat spreader assembly configured tolimit heat transfer between different heat transfer members within theheat spreader assembly.
 2. The thermal management system for themulti-chip-module as recited in claim 1, wherein each of the pluralityof lid structures is formed of a material having a thermal conductivityof at least 100 Watts per meter-Kelvin (W/m-K).
 3. The thermalmanagement system for the multi-chip-module as recited in claim 1,wherein each of the plurality of lid structures is formed of copper, oraluminum, or copper alloy, or aluminum alloy.
 4. The thermal managementsystem for the multi-chip-module as recited in claim 1, wherein eachthermal break that separates any two adjacent ones of the plurality oflid structures has a minimum heat transfer dimension greater than zeroand less than or equal to about 1 millimeter as measured between the twoadjacent ones of the plurality of lid structures.
 5. The thermalmanagement system for the multi-chip-module as recited in claim 1,wherein a vertical thickness of each of the plurality of lid structuresis greater than zero and less than or equal to about 1 millimeter. 6.The thermal management system for the multi-chip-module as recited inclaim 1, wherein the one or more heat sources within themulti-chip-module include at least one silicon photonics die or at leastone CMOS (Complementary Metal-Oxide Semiconductor) die.
 7. The thermalmanagement system for the multi-chip-module as recited in claim 1,wherein the one or more temperature sensitive components include atleast one III-V material die.
 8. The thermal management system for themulti-chip-module as recited in claim 1, wherein each of the pluralityof lid structures is configured to interface with a stiffener structureof the multi-chip-module.
 9. The thermal management system for themulti-chip-module as recited in claim 1, wherein at least one thermalbreak that separates two adjacent ones of the plurality of lidstructures is formed as a region of thermal interface material flowedinto the region between the two adjacent ones of the plurality of lidstructures during placement of the two adjacent ones of the plurality oflid structures on the multi-chip-module.
 10. The thermal managementsystem for the multi-chip-module as recited in claim 1, wherein at leastone thermal break that separates two adjacent ones of the plurality oflid structures is formed as a region of air.
 11. The thermal managementsystem for the multi-chip-module as recited in claim 1, wherein at leastone thermal break that separates two adjacent ones of the plurality oflid structures is formed as a solid material.
 12. The thermal managementsystem for the multi-chip-module as recited in claim 1, wherein theplurality of lid structures and any thermal break that separates twoadjacent ones of the plurality of lid structures are collectively formedas a single unit structure.
 13. The thermal management system for themulti-chip-module as recited in claim 1, wherein the plurality of lidstructures have substantially co-planar top surfaces.
 14. The thermalmanagement system for the multi-chip-module as recited in claim 13,wherein the heat spreader assembly includes a lower plate and an upperplate, with the plurality of separately defined heat transfer membersdisposed between the lower plate and the upper plate, the lower platepositioned in thermally conductive interface with the substantiallyco-planar top surfaces of the plurality of lid structures.
 15. Thethermal management system for the multi-chip-module as recited in claim14, wherein each of the plurality of separately defined heat transfermembers has a physical connection to at least one of the lower plate andupper plate, the lower plate and upper plate maintaining physicalpositions of the plurality of separately defined heat transfer membersrelative to each other.
 16. The thermal management system for themulti-chip-module as recited in claim 14, wherein each heat transfermember of the plurality of separately defined heat transfer members isseparated from each adjacent heat transfer member of the plurality ofseparately defined heat transfer members by a corresponding thermalbreak.
 17. The thermal management system for the multi-chip-module asrecited in claim 16, wherein each thermal break between any two heattransfer members of the plurality of separately defined heat transfermembers is vertical bounded by at least one of the lower plate and theupper plate.
 18. The thermal management system for the multi-chip-moduleas recited in claim 16, wherein at least one thermal break between anytwo heat transfer members of the plurality of separately defined heattransfer members is formed as a region of air.
 19. The thermalmanagement system for the multi-chip-module as recited in claim 16,wherein at least one thermal break between any two heat transfer membersof the plurality of separately defined heat transfer members is formedas a solid material.
 20. The thermal management system for themulti-chip-module as recited in claim 16, wherein at least one of thelower plate and the upper plate is perforated along at least one thermalbreak located between adjacent heat transfer members within the heatspreader assembly.
 21. The thermal management system for themulti-chip-module as recited in claim 14, wherein the lower plate has avertical thickness of less than or equal to about 1 millimeter, and theupper plate has a vertical thickness of less than or equal to about 1millimeter.
 22. The thermal management system for the multi-chip-moduleas recited in claim 14, wherein at least one of the plurality ofseparately defined heat transfer members is formed as a solid materialhaving a thermal conductivity of at least 200 Watts per meter-Kelvin(W/m-K).
 23. The thermal management system for the multi-chip-module asrecited in claim 14, wherein at least one of the plurality of separatelydefined heat transfer members is formed as a vapor chamber.
 24. Thethermal management system for the multi-chip-module as recited in claim14, wherein at least one of the plurality of separately defined heattransfer members is formed as a heat spreader plate with integrated heatpipes.
 25. The thermal management system for the multi-chip-module asrecited in claim 1, further comprising: a thermoelectric coolerpositioned in thermally conductive interface with the heat spreaderassembly, the thermoelectric cooler configured to overlie at least oneheat transfer member within the heat spreader assembly that ispositioned to overlie at least one lid structure of the plurality of lidstructures that is positioned to overlie one or more temperaturesensitive components within the multi-chip-module.
 26. The thermalmanagement system for the multi-chip-module as recited in claim 25,further comprising: a plurality of heat sink structures corresponding tothe plurality of heat transfer members within the heat spreaderassembly, the plurality of heat sink structures positioned torespectively overlie the plurality of heat transfer members within theheat spreader assembly, each of the plurality of heat sink structures inthermally conductive interface with either the heat spreader assembly orthe thermoelectric cooler.
 27. The thermal management system for themulti-chip-module as recited in claim 26, wherein the plurality of heatsink structures are configured and positioned physically separate fromeach other.
 28. The thermal management system for the multi-chip-moduleas recited in claim 26, wherein each of the plurality of heat sinkstructures is configured to have fin structures of substantiallyparallel orientation.